[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20070608123230.520655f5.akpm@linux-foundation.org>
Date: Fri, 8 Jun 2007 12:32:30 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: will_schmidt@...t.ibm.com
Cc: Anton Blanchard <anton@...ba.org>, linux-kernel@...r.kernel.org,
linuxppc-dev@...abs.org, Oleg Nesterov <oleg@...sign.ru>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 1/3] [PATCH i386] during VM oom condition, kill all
threads in process group
On Fri, 08 Jun 2007 14:19:18 -0500
Will Schmidt <will_schmidt@...t.ibm.com> wrote:
> > > > zap_other_threads() requires tasklist_lock.
>
> Yup, I missed that. Thanks for pointing it out.
>
> > > >
> > > > If we're going to do this then we should probably create some new function
> > > > (with a better name) which takes tasklsit_lock and then calls
> > > > zap_other_threads().
>
> I expect this will be a write_lock_irq() since zap_other_threads will be
> doing a bit more than just reading the task info.
No, I think read_lock() will be sufficient.
In fact, it's probably the case that rcu_read_lock() is now sufficient
locking coverage for zap_other_threads() (cc's people).
It had better be, because do_group_exit() forgot to take tasklist_lock. It
is perhaps relying upon spin_lock()'s hidden rcu_read_lock() properties
without so much as a code comment, which would be somewhat nasty of it.
You could perhaps just call do_group_exit() from within the fault handler,
btw.
> This will be down in a do-page-fault failure path (see
> arch/*/mm/fault.c). I wonder if calling write_lock is going to be safe,
> or if its possible to get into a deadlock? i.e. should I branch back up
> to the survive: label if I can't take the lock? Would that even be
> sufficient? or is it not an issue here?
You can take the lock in the fault handler. Nobody should be getting
pagefaults while holding tasklist_lock. (Well, a vmalloc fault might, but
that's a special-case which doesn't allocate memory or anything like that).
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists